The present invention relates to devices for obtaining blood samples from a patient, typically for diagnostic testing. More particularly, the invention relates a blood sampling assembly with a retractable needle to protect the health care worker from being inadvertently pricked by the needle after the blood withdrawal operation.
Various types of syringes have been devised over the past twenty years, including syringes intended to minimize or prevent the likelihood of the syringe needle pricking the operator during use. U.S. Pat. Nos. 4,790,827, 5,415,648, 6,193,695 and Re 33558 disclose various configurations for a safety syringe. In the ""695 Patent, a piston assembly is movable within the syringe body to create a vacuum which is used to withdraw the needle into the syringe. U.S. Pat. No. 6,126,618 discloses a complex device for obtaining blood from a patient, and is particularly designed to collect whole blood from a healthy donor.
Unique conditions are presented when devising a device for taking one or more blood samples while simultaneously protecting the health care worker from infection due to accidental contact with a contaminated needle. Blood samples are commonly obtained using a sterile device which is disposed after a single use. The blood sampling device ideally is simple to operate, is relatively economical to manufacture, is easy to use, and is highly reliable in its operation. In order to prevent the likelihood of infecting the health care worker by a needle prick, the needle may be withdrawn into the device so that the needle is protected from contacting the health care worker.
Conventional hypodermic syringes are less than desirable if blood is to be withdrawn from a patient for conducting diagnostic tests. The most widely used blood sampling devices use a cylinder with a double ended needle, which may be provided with a protective cap over one or both ends of the needle prior to use by the health care worker. The needle hub is conventionally threaded to the cylinder to locate the posterior needle end within the cylinder. The anterior end of the needle extending from the cylinder is inserted into the patient, and one or more evacuated tubes or vials are then positioned partially within the cylinder so that the opposing posterior end of the needle pierces through a stopper or membrane in the vial, thereby withdrawing blood into the vial. When the sample tube has been filled to its desired extent, the vial is withdrawn from the cylinder and, if desired, another vial is inserted into the cylinder to obtain another blood sample. By removing filled tubes and inserting new evacuated tubes, multiple samples can be taken without removing the anterior end of the needle from the patient. Double-ended needles are readily available from commercial sources. U.S. Pat. No. 6,017,317 discloses one type of assembly suitable for collecting various samples of blood in vacuum tubes.
Hospital and clinical practice requires that blood specimens be taken simply, quickly, and with inexpensive and readily disposable equipment. Many prior art blood sampling devices are intended to perform the function of minimizing the likelihood of an inadvertent needle stick, but the devices suffer from numerous drawbacks. Some devices require complex operations which render the devices unacceptable to many health care workers. Other devices themselves are relatively complex, thereby making the devices expensive to manufacture, particularly since the devices are preferably not reusable. Other devices require significant changes or modifications to conventional medical procedures, thereby requiring expensive and time consuming training.
U.S. Pat. Nos. 5,219,333 and 6,152,901 disclose blood collection devices which require that the operator move a slide along a cylinder to withdraw the needle into the cylinder. U.S. Pat. No. 4,643,199 discloses a blood sampling device which utilizes a combination of twisting and axial movements to secure a needle within the cylinder. U.S. Pat. No. 5,201,716 discloses a blood sampling device with a mechanism intended to eject the needle assembly from the cylinder. Other blood sampling devices with retractable needles are disclosed in U.S. Pat. No. 4,850,374 and 5,086,780. A blood collection device with a needle mounted eccentric relative to the cylinder is disclosed in U.S. Pat. No. 5,938,622.
U.S. Pat. No. 6,186,960 discloses a blood collection device which withdraws the needle into a vacuum tube after use. The device requires the health care worker to apply an axial force to break a mechanical connection between the cylinder and a needle seat. Accordingly the device is considered difficult to operate since the force required to break the mechanical connection is both significant and variable.
Accidental needle pricks typically result in the need for numerous blood tests for diseases such as HIV and hepatitis. Significant costs are incurred to test health care workers involved in taking blood samples, and unfortunately many health care workers have become infected with diseases transmitted when the blood sampling needle inadvertently pricks the health care worker.
The disadvantages of the prior art are overcome by the present invention, and an improved blood collection device is hereinafter disclosed which may be easily and reliably used by health care personnel. The device advantageously provides for the withdrawal of the needle into a vacuum tube by the mere rotation of the tube relative to the cylinder.
In an exemplary embodiment, the blood sampling assembly includes a double ended needle supported on a cylinder. The anterior end of the needle is intended for inserting into the patient, and the opposing posterior end of the needle is intended to perforate a stopper or membrane of an evacuated tube or vial placed in the cylinder.
In a preferred embodiment, the hollow cylinder has a needle end and an opposing extractor end. The evacuated tube or vial is thus inserted into the extractor end to perforate the stopper and fill the vial with blood. The cylinder includes circumferentially spaced needle seat tabs and needle seat slots each between spaced needle seat tabs. A needle seat is provided for supporting the needle on the cylinder, and includes circumferentially spaced cylinder tabs each in engagement with a respective needle seat tab to temporarily fix the needle seat to the cylinder. The needle seat also includes cylinder slots each between spaced cylinder tabs and circumferentially aligned with a respective needle seat tab to release the needle seat and the needle from the cylinder, as discussed subsequently.
An extractor assembly for positioning at least partially within the extractor end of the cylinder includes a closed end tube containing a vacuum, and a stopper in sealed engagement with an interior surface of the tube and axially movable between an initial position and a needle retracted position. When the tube is inserted into the cylinder, the stopper receives therein the posterior end of the needle. A stopper tab is axially secured to the stopper and engages the stopper tab stop on the cylinder to prevent rotation of the stopper tab when the tube is rotated. A stopper retainer is rotatable with the tube between a retaining position for temporarily fixing the stopper in the initial position and a release position for releasing the stopper to move to the needle retracted position. The stopper retainer includes a retainer tab in engagement with the stopper tab when the stopper retainer is in the retaining position and a slot in circumferential alignment with the stopper tab when the stopper retainer is in the release position. The extractor assembly further includes an end cap rotatable with the tube and a needle seat stop for engagement with the cap stop. Rotation of the tube rotates the end cap, the stopper retainer and the needle seat relative to the cylinder to release the needle seat and the stopper, so that the needle moves with the stopper to the needle retracted position by the vacuum within the tube.
In a preferred embodiment, the stopper retainer includes a cap stop and the cap includes a retainer stop, such that engagement of these stops prevents rotation of the stopper relative to the cap. The annular stopper retainer includes a throughbore for passing the needle seat through the stopper retainer when the stopper is moved to the needle retracted position. A similar throughbore is provided in the annular end cap. A stopper tab positioner engages both the stopper tab stop and the stopper tab to prevent rotation of the stopper tab during rotation of the tube.
According to the method of the invention, circumferentially spaced cylinder tabs on the needle seat each engage a respective needle seat tab to support the needle seat on the cylinder. The extractor assembly is inserted at least partially within the extractor end of the cylinder such that the opposed end of the needle is within or passes through the stopper. The health care worker then rotates the tube, which rotates the end cap and the stopper retainer from a retaining position to a release position, thereby releasing the needle seat from the cylinder and simultaneously releasing the stopper from the stopper retainer. The needle, the needle seat and the stopper move together as an assembly into the tube when the stopper moves to the needle retracted position by the vacuum within the tube.
It is an object of the present invention to provide an improved blood sampling assembly for retracting a needle and needle seat from a cylinder and thereby shielding the needle after completion of a blood collection procedure. It is a related object of the invention to provide a relatively inexpensive blood sampling assembly which significantly reduces the likelihood of the health care worker becoming pricked with the needle.
A related object of the invention is to provide a blood sampling assembly which utilizes a vacuum tube for withdrawing the needle into the vacuum tube upon rotation of the tube relative to the cylinder.
It is a feature of the present invention that the blood sampling assembly may be easily and reliably used to take various blood samples using a conventional evacuated vial, and thereafter the needle may be withdrawn into a vacuum tube for disposal.
Another feature of the invention is that the stopper may be positioned closely adjacent the end of the tube, so that substantially the full length of vacuum in the tube is available to retract the needle into the tube.
A significant advantage of the present invention is that the blood sampling assembly is relatively inexpensive, and uses techniques substantially similar to conventional techniques for obtaining blood samples.